I spent years making a website/webapp similar to metacritic, which aggregated new releases of new movies, games, apps etc, except the data was crowd-sourced, like wikipedia. It worked great and looked good. However, it never made more than a blip on the internet. It stuck around page 10 of google and I couldn't get any visiblity for it. And without being able to build a community it would never work so I had to pull the plug, which was very depressing. I wasted a large amount of my life working on that.